"Whispers of a Secret God" chronicles a clash of three sub-Saharan cultures battling for dominance in a tangle of drought, famine, and land rights. Slavery and dislocation have exacted a heavy toll, reshuffling ancient social boundaries and challenging long-held religious practices. Whereas stereotypical African villages evoke images of savagery, brutality, and superstition, the Fula tribes developed a more peaceful and rule-governed Muslim society. Honor and courage throbbed in their hearts.

The saga derives its title from the muddled vestiges of Christianity surviving from somewhere in...